Method of Producing Engine

The present application claims priority from Japanese Patent Application No. 2024-097754 filed on Jun. 17, 2024, the entire contents of which are hereby incorporated by reference.

The disclosure relates to a method of producing an engine including an auxiliary chamber.

For example, Japanese Unexamined Patent Application Publication (JP-A) No. H7-293249 discloses an engine including an auxiliary chamber. In JP-A No. H7-293249, an auxiliary-chamber structural body that forms the auxiliary chamber includes an upper member and a lower member that are each divided into two parts in a direction intersecting a central axis of a cylinder.

An aspect of the disclosure provides a method of producing an engine. The engine includes a partition member separating an auxiliary chamber from a main combustion chamber. The spacer is disposed in an inside of the partition member. The spark plug is mounted to the partition member. The partition member includes a cylindrical body, a hemispherical-shell-shaped end portion that is disposed at an end of the body, a first concave surface that is disposed at an inner surface of the end portion of the partition member, and an internal thread that is disposed on an inner peripheral surface of the body. The spacer has a second concave surface that is disposed on a side facing the first concave surface of the end portion of the partition member, and a first external thread that is disposed on an outer peripheral surface of the spacer and that is screwable to the internal thread of the body. The spark plug has a second external thread that is disposed on an outer peripheral surface of the spark plug and that is screwable to the internal thread of the body. The method includes: a first step of attaching the spacer to an inside of the body of the partition member by screwing the first external thread of the spacer and the internal thread of the body of the partition member to each other; and a second step of, after the first step, attaching the spark plug to the partition member by screwing the second external thread of the spark plug and the internal thread of the body of the partition member to each other.

In an engine including an auxiliary chamber, there is a desire to form the auxiliary chamber with a shape close to a spherical shape. An example of a method of producing the engine is a method of forming the auxiliary chamber by, for example, casting using a sand core or laser welding. However, in these producing methods, production costs are increased.

It is desirable to provide a method of producing an engine that makes it possible to suppress an increase in production costs.

An embodiment of the disclosure is described in detail below with reference to the attached drawings. Specific dimensions, materials, numerical values, and the like in the embodiment are merely exemplifications for making it easier to understand the disclosure, and, unless otherwise indicated, do not limit the disclosure. Note that in the specification and the drawings, elements having substantially the same functions and structures are given the same reference numerals to omit overlapping descriptions, and elements that are not directly related to the disclosure are omitted.

is a schematic top view schematically illustrating a structure of an engineaccording to an embodiment.is a first sectional view of the engineaccording to the embodiment along line II-II in.is a second sectional view of the engineaccording to the embodiment along line III-III in.

The engineis, for example, a reciprocating engine, and generates power by combustion of an air-fuel mixture. For example, the enginemay be installed in a vehicle and used as a drive source of the vehicle.

As illustrated in, the engineincludes a cylinder block, a cylinder head, and a piston. The cylinder blockincludes one or more cylinders. In, for convenience of explanation, one cylinderis exemplified. The cylinder headis coupled to the cylinder blockso as to cover the cylinder. The pistonis swingably accommodated in the cylinder.

A space surrounded by the cylinder, the piston, and the cylinder headis a main combustion chamberof the engine.

The cylinder headhas intake portsand exhaust ports. For example, as illustrated in, two intake portsand two exhaust portsmay be provided with respect to one cylinder.

The intake portsand the exhaust portsare coupled to the main combustion chamber. An intake valve (not illustrated) is provided at the intake ports. In accordance with the opening and closing of the intake valve, the intake portsguide to the main combustion chamberair that is supplied from the outside of the engine. An exhaust valve (not illustrated) is provided at the exhaust ports. In accordance with the opening and closing of the exhaust valve, the exhaust portsdischarge to the outside of the enginecombusted gas generated at the main combustion chamber.

The enginefurther includes a partition member, a spacer, and a spark plug. The engineincludes an injector (not illustrated) that supplies fuel to the main combustion chamber.

As illustrated in, the partition memberis provided at the cylinder head. As illustrated in, the partition memberis disposed at the cylinder headnear a central axis of the cylinder. The spark plugis mounted to the partition member. As illustrated in, the partition memberseparates an auxiliary chamberfrom the main combustion chamber.

is a partial enlarged sectional view illustrating the vicinity of the auxiliary chamberin an enlarged form. With reference to, structures related to the auxiliary chamberare described in detail below.

As illustrated in, the partition memberincludes a body, an end portion, a first concave surface, an internal thread, and ventilation ports.

The bodyhas a cylindrical shape. For example, the inside diameter of the bodymay change stepwise at a predetermined portion of the bodyin the direction of a central axis Cof the body. In more detail, the bodyincludes a small-diameter portion, a large-diameter portion, and a stepped portion. The inside diameter of the small-diameter portionis smaller than the inside diameter of the large-diameter portion. A central axis of the small-diameter portionand a central axis of the large-diameter portioncoincide with the central axis Cof the body. One end of the small-diameter portionin the direction of the central axis Cis continuous with one end of the large-diameter portionin the direction of the central axis Cwith the stepped portioninterposed therebetween.

The end portionhas a hemispherical shell shape at an end of the body. In more detail, the end portionis disposed at an end of the small-diameter portionon a side opposite to the large-diameter portion. The end portionis continuous with the small-diameter portionof the body. The hemispherical shell shape of the end portionis not limited to an example of a perfectly hemispherical shell shape (an outer surface or an inner surface is a perfectly hemispherical shape), and may be, for example, a substantially hemispherical shell shape, a semi-ellipsoidal shell shape, or a dome shell shape, as long as the shape includes a curved shell.

The first concave surfaceis disposed at the inner surface of the end portionof the partition member. The first concave surfacemay be a substantially hemispherical surface.

The internal threadis disposed on an inner peripheral surface of the body. In more detail, the internal threadis disposed on an inner peripheral surface of the small-diameter portion. The internal threadis formed from a stepped-portion--side end of the small-diameter portionto the vicinity of the end portionof the body.

The ventilation portsare formed through the end portionhaving the hemispherical shell shape. In the example of, two ventilation portsare provided in the partition member. However, the number of ventilation portsis not limited to two and may be one or three or more.

The spaceris disposed in the inside of the small-diameter portionof the bodyof the partition member. The spaceris a block having an outer peripheral surface whose cross-sectional shape is a circular shape. The spacerhas a second concave surface, a first external thread, and a through hole.

The second concave surfaceis disposed on a side facing the first concave surfaceof the end portionof the partition member. The second concave surfacemay be a substantially hemispherical surface. Note that each substantially hemispherical surface that is the first concave surfaceor the second concave surfaceis not limited to an example of one having a perfectly hemispherical shape, and may be, for example, one having a shape formed by cutting a part of a spherical surface, a semi-ellipsoidal surface, or a dome curved surface, as long as the surface is curved.

The auxiliary chamberis a space surrounded by the first concave surfaceof the end portionof the partition member, the inner peripheral surface of the bodyof the partition member, and the second concave surfaceof the spacer. The auxiliary chamberis, for example, a space like a short circular cylinder being interposed between two hemispheres. The spaceris disposed at a position where the capacity of the auxiliary chamberbecomes a previously provided design-based capacity.

Note that the auxiliary chambermay be formed by the first concave surfaceand the second concave surfacealone without using the inner peripheral surface of the body. In this case, an end-portion--side end of the spacermay be positioned at an end-portion--side end of the body, and the auxiliary chambermay be formed to have a substantially spherical shape.

In the engineof the embodiment, by forming the first concave surfaceat the end portionof the partition memberand by forming the second concave surfaceat the spacer, a mixture can smoothly flow in the auxiliary chamberas indicated by arrow Ain.

The first external threadis disposed on the outer peripheral surface of the spacer. The first external threadis capable of being screwed to the internal threadof the bodyof the partition member. By screwing the first external threadof the spacerto the internal threadof the partition member, the spaceris attached to the inside of the partition member.

Although described below, the spaceris inserted into the partition memberfrom a side of the partition memberopposite to the end portion. The first external threadof the spacerand the internal threadof the bodyare screwed to each other from the stepped-portion--side end of the small-diameter portionof the body.

Here, a target position of the spacerwhen the spaceris to be attached is a position of the spacerwhere the capacity of the auxiliary chamberbecomes a previously provided design-based capacity. The internal threadof the bodyhas a length that, when the spacerreaches the target position in the inside of the partition member, allows the first external threadof the spacerto be tightened and stopped with respect to the internal threadof the bodyof the partition member.

Therefore, in the engineof the embodiment, by simply screwing and tightening the threads until the spaceris tightened and stopped, the spacercan be disposed at the target position.

The through holeis formed in the direction of the central axis Cof the bodyof the partition member, in other words, the direction of a central axis of the spacer.

is a plan view of the spacerwhen seen from a first-concave-surface-side of the partition member. As illustrated in, the cross-sectional shape of the through holeof the spaceris a hexagonal shape.

Therefore, in the engineof the embodiment, a hexagonal wrench can be inserted into the through hole of the spacer. Consequently, in the engineof the embodiment, the first external threadof the spacercan be easily screwed to the internal threadof the bodyof the partition memberby using the hexagonal wrench inserted into the through holeof the spacer.

Note that the cross-sectional shape of the through holeof the spaceris not limited to a hexagonal shape, and may be any shape as long as the shape has three or more vertices, such as a triangular shape, a square shape, an octagonal shape, or a star shape. The cross-sectional shape of the through holeof the spaceris, preferably, a predetermined shape, and is, more preferably, a predetermined polygonal shape. “Predetermined shape” is a shape previously set in accordance with the shape of a tool for attaching the spacer, and “predetermined polygonal shape” is a polygonal shape previously set in accordance with the polygonal shape of the tool. That is, when a tool having a special cross-sectional shape is used, the cross-sectional shape of the through holeof the spacermay be a predetermined shape in correspondence with the shape of the tool.

In the engineof the embodiment, when the cross-sectional shape of the through holeof the spaceris a predetermined polygonal shape, if a tool having a shape corresponding to the polygonal shape is used, the first external threadof the spacercan be easily screwed to the internal threadof the body of the partition member.

The spark plugincludes a second external threadand an electrode. The second external threadis disposed on an outer peripheral surface of the spark plug. The second external threadcan be screwed to the internal threadof the small-diameter portionof the body.

Although described below, the spark plugis attached to the partition memberfrom a side of the partition memberopposite to the end portion. The second external threadof the spark plugand the internal threadof the bodyare screwed to each other from the stepped-portion--side end of the small-diameter portionof the body.

In the engineof the embodiment, both the first external threadof the spacerand the second external threadof the spark plugcan be screwed to the internal threadof the body. Therefore, in the engineof the embodiment, the spacerand the spark plugcan be attached in substantially the same way, and thus the spacercan be attached in a simplified manner.

When the spark plugis mounted to the bodyof the partition member, the electrodeof the spark plugis inserted into the through holeof the spacer. An end of the electrodeof the spark plugmay be exposed to the auxiliary chamber.

As illustrated in, a predetermined electrical wiremay be coupled to a side of the spark plugopposite to the auxiliary chamber. The cross-sectional shape of an end of the spark plugon a side opposite to the auxiliary chambermay be, for example, a hexagonal shape.

As illustrated in, the cylinder headincludes a mounting portionto which the partition memberis mounted. The mounting portionmay have a key groove. In this case, the partition membermay include a projecting key portionin correspondence with the key groove. The key portionmay be, for example, a part of an outer peripheral surface of the large-diameter portionof the body.

Therefore, when the partition memberis to be mounted to the cylinder head, by fitting the key portionof the partition memberto the key grooveof the mounting portionof the cylinder head, the partition membercan be easily positioned.

As illustrated in, the partition membermay be fixed to the cylinder headby a fixing member. The fixing membermay include a bolt. For example, the large-diameter portionof the bodyof the partition membermay be provided with a flange, and the flangemay be fixed to the cylinder headby the bolt serving as the fixing member.

As illustrated in, the partition memberis provided with respect to the cylinder headsuch that the end portionof the partition memberis exposed to the main combustion chamber. As illustrated in, the ventilation portscause the main combustion chamberand the auxiliary chamberto communicate with each other.

Air and fuel supplied to the main combustion chamberare supplied to the auxiliary chamberthrough the ventilation ports. The air and the fuel supplied to the auxiliary chamberare sufficiently mixed in the auxiliary chamber. The spark plugignites the mixture in the auxiliary chamberto combust the mixture. Explosion caused by the combustion of the mixture is transmitted to the main combustion chamberthrough the ventilation ports. The explosion of the mixture in the main combustion chambercauses the pistonto slide.

is a flowchart illustrating the flow of a method of producing the engineaccording to the embodiment. For convenience of explanation, the method of producing the engineaccording to the embodiment may be called the producing method.

As illustrated in, the producing method includes a partition member attaching step (S), a spacer attaching step (S), and a plug attaching step (S). Each step of the producing method may be performed by a human being, or by a machine, or by both a human being and a machine.

In the partition member attaching step (S), the partition memberis attached to the cylinder headof the engine. In more detail, in the partition member attaching step (S), the partition memberis accommodated in the mounting portionof the cylinder headof the engine. Here, by fitting the key portionof the partition memberto the key grooveof the mounting portion, the partition memberis positioned with respect to the cylinder head. By using the bolt serving as the fixing member, the flangeof the partition memberis fixed to the cylinder head. In this way, the partition memberis mounted to the cylinder head.

After the partition member attaching step (S), the spacer attaching step (S) is performed. In the spacer attaching step (S), by screwing the first external threadof the spacerand the internal threadof the bodyof the partition memberto each other, the spaceris attached to the inside of the bodyof the partition member.